Thermal inkjet printers typically utilize a printhead that includes an array of orifices (also called nozzles) through which ink is ejected on to paper or other print media. One or more printheads may be mounted on a movable carriage that traverses back and forth across the width of the paper feeding through the printer, or the printhead(s) may remain stationary during printing operations, as in a page width array of printheads. A printhead may be an integral part of an ink cartridge or part of a discrete assembly to which ink is supplied from a separate, often detachable ink container. Ink filled channels feed ink to a firing chamber at each orifice from a reservoir ink source. Applied individually to addressable thermal elements, such as resistors, ink within a firing chamber is heated, causing the ink to bubble and thus expel ink from the chamber out through the orifice. As ink is expelled, the bubble collapses and more ink fills the chamber through the channels from the reservoir, allowing for repetition of the ink expulsion sequence.
Many conventional thermal inkjet printheads are currently produced with ink feed channels formed in a semiconductor substrate structure that includes the firing resistors. A barrier layer is formed on the substrate structure and a metal or polyimide (e.g., Kapton®) orifice plate is attached to the barrier layer. The ink feed channels carry ink to openings in the barrier layer that direct ink to the resistors and partially define the firing chamber volume for each resistor. The barrier layer material is usually a thick, organic photosensitive material laminated onto the substrate structure, and then patterned and etched with the desired opening and chamber configuration. The orifice plate provides the ink ejection/expulsion path for the firing chambers. Metal and polyimide orifice plate materials and organic barrier layer materials, however, can be susceptible to corrosion from printing inks, thus potentially limiting the ink chemistry options for better printing performance
Also, during printhead fabrication, aligning and attaching the orifice plate to the barrier layer on the substrate structure requires special precision and special adhesives. If the orifice plate is warped or dimpled, or if the adhesive does not correctly bond the orifice plate to the barrier layer, poor control of the ink drop trajectory may result. Often, individual orifice plates must be attached at single printhead die locations on a semiconductor substrate wafer/structure that contains many such die locations. It is desirable, of course, for increasing productivity as well as helping ensure proper orifice plate alignment to have a fabrication process that allows for placement of a single orifice plate over the entire substrate structure to cover all of the printhead die locations. Some efforts to fabricate orifice plates from a deposited dielectric material have met with only limited success due to high dielectric deposition temperatures and large built-in stresses for thick dielectric layers.
The structures shown in the figures, which are not to scale, are presented in an illustrative manner to help show pertinent structural and processing features of the disclosure